Conversion of adamantane hydrocarbons to monools

ABSTRACT

ADAMANTANE HYDROCARBONS OF THE C10-C30 RANGE HAVING AT LEAST ONE UNSUBSTITUTED BRIDGEHEAD POSITION ARE ADMIXED WITH FUMING SULFURIC ACID(102-112% H2SO4 EQUIVALENT) AT A TEMPERATURE BETWEEN THE FREEZING POINT OF THE ACID AND 50*C. TO EFFECT DISSOLUTION AND THE MIXTURE IS THEN REACTED WITH WATER TO FORM BRIDGEHEAD MONOOLS CORRESPONDING TO THE STARTING HYDROCARBONS.

United States Patent 3,646,224 CONVERSION OF ADAMANTANE HYDRO- CARBONS TO MONOOLS Robert E. Moore, Wilmington, DeL, assignor to Sun Oil Company, Philadelphia, Pa. N Drawing. Filed Dec. 17, 1968, Ser. No. 784,487 Int. Cl. C07c 35/44 US. Cl. 260-617 F 14 Claims ABSTRACT OF THE DISCLOSURE Adamantane hydrocarbons of the C C range having at least one unsubstituted bridgehead position are admixed with fuming sulfuric acid (102-1 12% H 50 equivalent) at a temperature between the freezing point of the acid and 50 C. to eflect dissolution and the mixture is then reacted with Water to form bridgehead monools corresponding to the starting hydrocarbons.

BACKGROUND OF THE INVENTION As shown, the bridgehead carbon atoms customarily are designated by the numerals 1, 3, 5 and 7, respectively.

The preparation of methyland/or ethyl-substituted adamantanes by the isomerization of tricyclic naphthenes by means of an aluminum halide or HFBF catalyst has been described by several references including the following: Schneider US. Pat. No, 3,128,316, dated Apr. 7, 1964; Janoski and Moore US. Pat. No. 3,275,700, dated Sept. 27, 1966; Schleyer et al., Tetrahedron Letters No. 9, pp. 305-309 (1961); and Schneider et al., J. A. C. 5., vol. 86, pp. 5365-5367 (1964). The isomerization products can have the methyl and/ or ethyl groups attached to the adamantane nucleus at either bridgehead or nonbridgehead positions or both, although completion of the isomerization reaction favors bridgehead substitution. Examples of alkyladamantanes made by such isomerization are methyladamantanes, dimethyladamantanes, ethyladamantanes, methylethyladamantanes, dimethylethyladamantanes and trimethyladamantanes.

Preparations of adamantanes hydrocarbons having higher alkyl substituents have been described in the following references: Schneider US. Pat. No. 3,382,288, dated May 7, 1968; Spengler et al., Erdol und Kohle- Erdgas-Petrochemie, vol. 15, pp. 702-707 (1962); and Hoek et al., 85 (1966), Recueil, 10451053.

Procedures for converting adamantane hydrocarbons to bridgehead hydroxy derivatives have been described in the prior art. Schneider US. Pat. No. 3,356,740, dated Dec. 5, 1967, discloses the conversion of alkyladamantanes to bridgehead alcohols by air oxidation using a soluble metallic organic salt as catalyst. In I. Org. Chem,

3,646,224 Patented Feb. 29, 1972 'ice vol. 26, pp. 22072212 (1961), the air oxidation of adamantane itself in the presence of a peroxide catalyst is described. Moore US. Pat. No. 3,383,424, dated May 14, 1968, shows the oxidation of adamantane and alkyladamantanes by means of chromic acid in aqueous acetic acid under conditions to produce either monools or diols.

SUMMARY OF THE INVENTION DESCRIPTION The process of the invention more particularly comprises:

(a) establishing an admixture consisting essentially of a saturated adamantane hydrocarbon of the C -C range having 1 to 4 unsubstituted bridgehead carbon atoms and fuming sulfuric acid having a strength corresponding to 102l12% H SO equivalent by weight, the temperature of the admixture being between the freezing point of the acid and 50 C.;

(b) mixing the admixture at said temperature until at least a substantial proportion of the hydrocarbon has dissolved in the acid;

(c) and reacting the admixture with water to form a bridgehead monool corresponding to the starting adamantane hydrocarbon.

The process appears to involve a carbonium ion reaction which can be illustrated by considering, for example, the conversion of 1,3-dimethyladamantane (for convenience, DMA) to its corresponding alcohol, as follows (non-reacting hydrogen atoms being omitted for simplicity) Steps (a) (fuming sul- C C C C and furlc acid) H Step (c):

As illustrated by the equations the mechanism is visualized as involving the abstraction of a bridgehead hydrogen atom by means of the fuming sulfuric acid to form a DMA carbonium ion. While the hydrocarbon itself is not very soluble in the acid phase, the carbonium ion is and the hydrocarbon material thus becomes solubilized as mixing occurs in steps (a) and (b). When the mixture is then diluted with water, the Water immediately reacts with the carbonium ion to form the desired bridgehead monool. The latter precipitates and can be recovered from the aqueous acid by filtration.

The invention can be used to prepare bridgehead monools from adamantane or any saturated adamantane hydrocarbon of the C C range having one or more alkyl and/or cycloalkyl substituents provided that the nucleus has at least one unsubstituted bridgehead position. The alkyl or cycloalkyl substituents can be located at other bridgehead positions of the nucleus or at non-bridgehead positions or both, and such substituents are substantially unaffected at the relatively low temperatures and short reaction times employed in the present process. The following are some specific examples of starting materials: adamanatane; l-methyl or Z-methyladamantane; 1,2- 1,3- or 1,4-dimethyladamantane; 1- or Z-ethyladamantane; 1- ethyl-S-methyladamantane; 1-ethyl-3,S-dimethyladamantane; 1,3,5 trimethyladamantane; nonbridgehead trimethyladamantanes; diethyladamantanes; 1 n propyl or l-isopropyladamantane; l-methyl 2 propyladamantane; l n butyladamantane; 1,3-di-n-pentyladamantane; lcyclopentyl or l-cyclohexyladamantane; l-methyl-S-heptyladamantane; l-n-decyladamantane; l-n-decyl-3-ethyladamantane; 1,3-dicyclohexyladamantane; l n hexadecyladamantane; 1,3,5 dicyclopentyladamantane; leicosyladamantane and the like. Other examples can be found in the references cited above.

The strength of the fuming sulfuric acid used in the process should be in the range of 102-112% H 80 equivalent by weight and preferably IDES-108% H 80 equivalent. Preferably enough fuming acid is used to provide at least two moles of S per mole of the starting adamantane hydrocarbon and more preferably an amount substantially in excess of such proportion is employed. On a volume basis, proportions generally used are in the range of 1:1 to :1 volumes of the fuming acid per volume of adamantane hydrocarbon.

The reaction of steps (a) and (b) as shown in the foregoing equation is carried out at relatively low temperature and the reaction time preferably is minimized to prevent the formation of substantial amounts of byproducts. The temperature employed is between the freezing point of the fuming acid (circa 8l0 C.) and 50 C. and preferably is in the lower part of this range, e.g. below C.

When the adamantane hydrocarbon and the fuming acid are first admixed, a two-phase system is formed since the hydrocarbon itself has a relatively low solubility in the acid. However the hydrocarbon material becomes solubilized in the acid as it converts to the carbonium ion form, and this conversion will cause all of it to go into solution if sufiicient mixing time is allowed. Mixing of the admixture is carried out until at least a substantial proportion of the adamantane hydrocarbon has dissolved in the acid and preferably until substantially all of it has dissolved. In order to minimize by-product formation, water is then immediately added to react as shown for step (c), whereupon all of the material of carbonium ion form is converted to the corresponding monool. On the other hand, if the solubilized material is allowed to stand for a time before the water is added, the chances of forming undesired by-products are increased since the carbonium ion material may be capable of undergoing reactions leading to other products.

In order to minimize the time in steps (a) and (b), vigorous mixing is advantageous so as to effect good contact between the phases. This reduces the time necessary for bringing the hydrocarbon material into solution in the acid phase. The rate at which dissolution occurs will vary depending upon the particular adamantane hydrocarbon used as feed. The adamantane hydrocarbons which are solids at the reaction temperature employed, such as adamantane or l-methyladamantane, tend to become solubilized more slowly than the liquid alkyladamantanes, such as Z-methyladamantane, 1- or Z-ethyladamantane, any of the dimethyladamantanes, ethylmethyladamantanes, trimethyladamantanes, or tetramethyladamantane having one or more nonbridgehead methy groups. Also, as the molecular weight of the feed hydrocarbon is increased, the rate of dissolution in the fuming acid tends to decrease and longer mixing times are required to efifect complete solution. In cases when a normally solid adamantane hydrocarbon is used as feed, it is advantageous to add it to the acid in the form of finely divided powder to facilitate solubilization.

As soon as all or at least a substantial amount of the feed hydrocarbon has dissolved in the fuming acid, the

reaction mixture is admixed with cold water or ice to effect the reaction of step (c). This should be done with adequate cooling to prevent an inordinate rise in temperature. The proportion of water added should be sufiicient to reduce the acid strength to less than 60% H and, if desired, to considerably less than this level. Dilution of the mixture in this manner causes immediate formation of the monool which is insoluble in the aqueous acid and precipitates. The resulting alcohol can be recovered by filtration and then can be purified by recrystallization from a suitable solvent such as pentane, hexane or petroleum ether. Based on the adamantane hydrocarbon consumed, yields above generally can be obtained, particularly if low reaction temperatures (e.g., 10-20" C.) are used.

The following examples are specific illustrations of the invention:

Example I This example shows the conversion of 1,3-dimethyladamantane (DMA) to the corresponding bridgehead alcohol. ml. of 20% fuming sulfuric acid (104.5% H 30 equivalent) were cooled to a temperature of about 10 C. by immersion in an ice bath, 10 g. of DMA (-M.P.=30 C.) were added thereto and the mixture was then rapidly stirred at about 10 C. for approximately 5 minutes, by which time almost all of the DMA had gone into solution. The mixture was poured over a relatively large volume of ice, the thus diluted mixture was extracted with diethyl ether and the ether was evaporated. The resulting crude product upon analysis by VPC showed the following composition:

=Percent l-hydroxy DMA 9:6.5 Unreacted DMA 11.8 By-products 1.7

This product was recrystallized from petroleum ether and 1-hydIoxy-3,S-dimethyladamantane having a melting point of about 97 C. was obtained. The yield was 95%.

Example H In this example the starting hydrocarbon was 'l-ethyl- 3,5-dimethyladamantane (EDMA) which melts below '80 C. The reaction was run under the same conditions as described in Example I except that the time of mixing was increased to 10 minutes. The crude product obtained by analysis of the ether extract had the following composition:

Percent l-hydroxy-EDMA 81.8 Unreacted EDMA 17.0 By-products 1.2

Upon purification of the product by recrystallization from petroleum ether, l-hydroxy-E-DMA was obtained having a melting point of about 85 C. The yield of this monool was about 98.5% based on BDMA consumed.

Comparison of Example II with Example I indicates that the rate of dissolution of the liquid adamantane hydrocarbons in the fuming acid increases as the hydrocarbon molecular weight increases.

Example III Example II was repeated except that adamantane was substituted for EDMA, the solid adamantane being added to the fuming acid as a powder. It was found that in the 10 minutes reaction time allowed only 10% of the adamantane was converted to l-adamantanol. This was due to the slower rate of dissolution of the solid adamantane in the fuming acid; most of the adamantane had not gone into solution during the time permitted. 'Essentially no reaction products other than l-adamantanol were formed.

When other adamantane hydrocarbons as herein specified are substituted for those used in the foregoing exampics, analogous results are obtained, However, in view of the decrease in rate of dissolution as the molecular weight of the adamantane hydrocarbon feed increases, as shown by comparing Examples I and II, and in further view of the fact that lower molecular weight adamantane hydrocarbons are generally more readily available, the invention will have its most utility in the conversion of adamantanes of the C -C range.

The use of other acid strengths and other temperatures within the limits herein described also results in effective conversion of the specified adamantane hydrocarbons to the corresponding bridgehead monools.

The invention claimed is:

1. Method of converting adamantane hydrocarbons to bridgehead monools which comprises:

(a) establishing an admixture consisting essentially of a saturated adamantane hydrocarbon of the C -C range having 1 to 4 unsubstituted bridgehead carbon atoms and fuming sulfuric acid having a strength corresponding to -102-112% H 50 equivalent by weight, the temperature of the admixture being between the freezing point of the acid and 50 C.;

(b) mixing the admixture at said temperature until at least a substantial proportion of the hydrocarbon has dissolved in the acid;

(c) and reacting the admixture with water to form a bridgehead monool corresponding to the starting adamantane hydrocarbon.

2. Method according to claim 1 wherein the temperature is less than C.

3. Method according to claim 2 wherein said strength corresponds to l03-l08% H 50 4. Method according to claim 1 wherein said strength corresponds to 103108% H 5. Method according to claim 1 wherein said adamantane hydrocarbon is of the C -C range.

6. Method according to claim 5 wherein the starting adamantane hydrocarbon is selected from the group consisting of adamantane, methyladamantanes, dimethyladamantanes, ethyladamantanes, methylethyladamantanes, dimethylethyladamantanes and trimethyladamantanes.

7. Method according to claim 6 wherein said strength corresponds to 103108% H 80, and the temperature is less than 25 C.

8. Method according to claim 5 wherein said strength corresponds to 103-108% H 50 and the temperature is less than 25 C.

9. Method according to claim 1 wherein said adamantane hydrocarbon is a C C alkyladamantane, the mixing thereof with said acid in step (b) is continued until substantially all of the adamantane hydrocarbon has dis solved in the acid, and the admixture is then reacted with water before substantial lay-product formation can occur.

10. Method according to claim 9 wherein said strength corresponds to 103108% H and the temperature is less than 25 C.

11. Method according to claim 10 wherein the starting adamantane hydrocarbon is selected from the group consisting of adamantane, methyladamantanes, dimethyladamantanes, ethyladamantanes, methylethyladamantanes, dimethylethyladamantanes, and trimethyladamantanes.

12. Method according to claim 11 wherein the starting adamantane hydrocarbon is 1,3-dimethyladamantane; rl-ethyladamantane; l-ethyl-3-methyladamantane; 1,3,5- trimethyladamantane or l-ethyl 3,5 dimethyladamantane.

13. Method according to claim 1 wherein the starting adamantane hydrocarbon is 1,3-dimethyladamantane; l-ethyladamantane; 1-ethyl-3-methyladamantane; 1,3,5- trimethyladamantane or l-ethyl 3,5 dimethyladamantane.

14. Method according to claim 13 wherein the temperature is less than 25 C., said strength corresponds to 103108% H the mixing in step (b) is continued until substantially all of the adamantane hydrocarbon has dissolved in the acid, and the admixture is then reacted with water before substantial byproduct formation can occur.

References Cited Geluk et al.: Tetrahedron, vol. 24, pp. 5361-5368 (August 1968).

Gillespie et al.: Quarterly Review, vol. 8, N0. 1, pp. 4042 (1954).

Olah et al.: J. Am. Chem. Soc., vol. 86, pp. 11368-41369 (.1964).

LEON ZITVER, Primary Examiner M. W. GLYNN, Assistant Examiner US. Cl. X.R. 

